Did Florida’s Stand Your Ground Law Increase Firearm Homicides?

At least two empiricalpapers have found that Stand Your Ground (SYG) laws like the one in Florida are associated with an average increase rather than a decrease in firearm homicides. This plausibly occurs because the deterrent effects of such laws are outweighed by the increase in the range of legal defenses for the use of lethal violence that become available to attackers. While SYG laws are meant to protect defenders, the absence of impartial witnesses makes it difficult in many cases to determine who ought to have had a “reasonable fear” of whom.

Anton Strezhnev (a former student and current co-author of mine) provides some interesting additional evidence for the Florida case. You should read his full post to comprehend the methodology used (based on the synthetic control method) but here is his description of the graph above:

The figure above plots the gap in firearm homicide rates between the actual time series and the estimated synthetic control for Florida and for each of the control states. Relative to the distribution of relevant placebos, the Florida effect stands out post-2006. Florida’s is the most unusual line in the set and from 2007-2010 shows a positive deviation from the control greater than any of the placebo tests. Although the pool of control states is somewhat small, limiting the number of possible placebo tests, the trajectory of Florida’s homicide rate is certainly unusual and difficult to attribute to pure chance.

So, compared to a group of states that had similar homicide rates prior to 2005, Florida’s homicide rate shot up unusually after 2005 (and in a way that cannot easily be accounted for by observed variables). One can never definitively proof a causal effect with aggregate data of this type but the data appear consistent with the claim that this law has not served the purpose of reducing homicides.

It’s not clear what these data show … I’d think that if these additional homocides are justifiable, and replacing, say, rapes, aggravated assaults, etc, then many (most?) supporters would see this as fulfilling its purpose.

This is an interesting first cut, but we need to know much more about the data to say anything about the policy implications.

well, a good place to start would be the discussion of the data in the papers linked.

use state-level mortality data from the CDC’s Wonder database to construct a measure of per-capita firearm homicides for each state in years 2000 to 2010. Following the lists in Cheng/Hoekstra and McClellan/Terkin I also obtain a set of state-level covariates from Census, BLS and DOJ data sources related to age and racial composition of the population, poverty, median income, urbanization, unemployment, incarceration, and federal police presence. All of the covariates are measured in 2000 – prior to the start of the time-series.

I address this briefly in the post. While Florida’s aggravated assault/violent crime rate has declined since 2000, it is difficult to construct a plausible counterfactual match using the synthetic control approach simply because its assault rates are substantially higher than any of the states in the control pool. Any match would rely heavily on extrapolation.

That being said, when I do try to create a “best possible” synthetic match on aggravated assaults, there is no clear downward trend after 2005 relative to the control. In contrast to the clear pattern exhibited by firearm homicides, the pattern for aggravated assault more or less follows the trend of the placebos.

Excuse me, but I believe you’re talking about 2 things. First, did stand your ground displace other crimes by shifting aggravated assault, etc. to death? Second, the conflation of potential shifting with “deterrence”. The first is not an answer to the second.

To address the second, the point of the law is to reduce violence, not shift it. The idea is that availability of guns and the relative freedom to use deadly force when threatened would reduce the number of times people would attack others. That is the blunt notion behind the sort of guns everywhere mentality: if everyone has a gun, then everyone is protected because no one can be a victim. Even if the incidents shifted – which doesn’t seem to have happened – the data shows the law failed to accomplish that fundamental goal.

Perhaps this is another cut at the question Adam is raising: if the “homicides” category includes justifiable homicides, then defenders of SYG might see nothing wrong with the spike provided that the spike is in justifiable homicides. This is true whether or not rates of other felonies drop.

In other words, defenders of SYG are *not*, I think, principally interested in reducing numbers of homicides — they’re interested in who gets killed. If the bump in homicides are “bad guys” then that’s good, from their perspective.

But then SYG ought to be shifting homicides from murders to justifiable homicide. If an SYG law converts a case in which a bad guy kills a good guy to a case where a good guy kills a bad guy, then it doesn’t increase the total number of homicides. And if it creates a good guy-on-bad guy homicide where there wouldn’t have been a bad guy-on-good guy homicide, then it’s not achieving its stated purpose, because the “good guy” wasn’t actually threatened. At the very least we should see a drop in attempted homicides or assaults in which the perpetrator is not killed.

Unless, of course, SYG proponents have divided people up into “good guys” and “bad guys” irrespective of their behavior and are indifferent to the deaths of the “bad guys” even where they pose no actual threat to “good guys.” Those would be the SYG proponents who think that the system is working just fine.

I don’t think that’s right. Maybe it’s turning cases of “breaking and entering” (B/E) into a B/E plus a (justifiable ) homicide: bad guy breaks in, bad guy’s dead. Then you get the same number of B/Es plus a homicide, and the law is working exactly as intended by its supporters.

More generally, the law could be having a variety of effects at the same time: (1) deterring some crimes, (2) adding justifiable homicides to some crimes as in the example above, (3) switching some unjustified homicides into justified ones (when the good guy shoots first to prevent the bad guy from doing same), and (4) causing homicides where they otherwise wouldn’t have happened absent SYG. All but the last of those effects would have been exactly as the proponents would have wanted, and yet the net effect could be entirely consistent with the observed data. Depending on the relative size of effects 1-3 vs. 4 (and — you’ll hate this — depending on whether the homicides in #4 are bad guy vs. good guy, or bad guy on bad guy) the law might be a great success.

To be clear, I haven’t seen this data and have no strong prior about this. I was just agreeing with the thrust of Adam’s skeptical comment, above, namely that I don’t see that a spike in homicide rates per se does much to help us sort out the effectiveness or lack thereof of SYG.

It’s not the traditional penalty…*after the fact*. That is, if we’ve apprehended the person, and he’s no longer threatening anyone, we (thankfully) apply lesser penalties.

But during the commission of the crime that’s a different matter, because the person committing the B/E’s intentions can often reasonably be inferred to be threatening to life as well as property.

If more fine-grained data analysis revealed that SYG was leading to lots of homicides because robbers were getting shot (and I have no reason to believe that’s what is actually going on in the data) then I think you’d have SYG laws in 40 states in no time.

I thought the innovation of SYG was that it applied outside the home, killing home intruders in your home is already covered under self defense provisions. Isn’t SYG supposed to make it easier to claim self defense when you kill someone in a public place? So the breaking and entering should not be affected one way or the other.

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